/* $begin tinymain */
/*
 * tiny.c - A simple, iterative HTTP/1.0 Web server that uses the
 *     GET method to serve static and dynamic content.
 *
 * Updated 11/2019 droh
 *   - Fixed sprintf() aliasing issue in serve_static(), and clienterror().
 */
#include "csapp.h"

void doit(int fd);
void read_requesthdrs(rio_t *rp);
int parse_uri(char *uri, char *filename, char *cgiargs);
void serve_static(int fd, char *filename, int filesize);
void get_filetype(char *filename, char *filetype);
void serve_dynamic(int fd, char *filename, char *cgiargs);
void clienterror(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg);
void echo(int connfd);
int main(int argc, char **argv)
{
    int listenfd, connfd;
    char hostname[MAXLINE], port[MAXLINE];
    socklen_t clientlen;
    struct sockaddr_storage clientaddr;

    /* Check command line args */
    if (argc != 2) {
        fprintf(stderr, "usage: %s <port>\n", argv[0]);
        exit(1);
    }

    listenfd = Open_listenfd(argv[1]);
    while (1) {
        clientlen = sizeof(clientaddr);
        connfd = Accept(listenfd, (SA *)&clientaddr, &clientlen);  // line:netp:tiny:accept
        Getnameinfo((SA *)&clientaddr, clientlen, hostname, MAXLINE, port, MAXLINE, 0);
        printf("Accepted connection from (%s, %s)\n", hostname, port);
        echo(connfd);
        Close(connfd);  // line:netp:tiny:close
    }
}
void echo(int connfd)
{
    rio_t read;
    Rio_readinitb(&read, connfd);
    char buf[MAXLINE];
    size_t n = Rio_readlineb(&read, buf, MAXLINE);
    Rio_writen(connfd, buf, n);
    for (; strcmp(buf, "\r\n");) {
        n = Rio_readlineb(&read, buf, MAXLINE);
        Rio_writen(connfd, buf, n);
    }
}

/*
 * doit - handle one HTTP request/response transaction
 */
/* $begin doit */
void doit(int fd)
{
    int is_static;
    struct stat sbuf;
    char buf[MAXLINE], method[MAXLINE], uri[MAXLINE], version[MAXLINE];
    char filename[MAXLINE], cgiargs[MAXLINE];
    rio_t rio;

    /* Read request line and headers */
    Rio_readinitb(&rio, fd);
    if (!Rio_readlineb(&rio, buf, MAXLINE))  // line:netp:doit:readrequest
        return;
    printf("%s", buf);
    sscanf(buf, "%s %s %s", method, uri, version);  // line:netp:doit:parserequest
    if (strcasecmp(method, "GET")) {                // line:netp:doit:beginrequesterr
        clienterror(fd, method, "501", "Not Implemented", "Tiny does not implement this method");
        return;
    }                        // line:netp:doit:endrequesterr
    read_requesthdrs(&rio);  // line:netp:doit:readrequesthdrs

    /* Parse URI from GET request */
    is_static = parse_uri(uri, filename, cgiargs);  // line:netp:doit:staticcheck
    if (stat(filename, &sbuf) < 0) {                // line:netp:doit:beginnotfound
        clienterror(fd, filename, "404", "Not found", "Tiny couldn't find this file");
        return;
    }  // line:netp:doit:endnotfound

    if (is_static) {                                                  /* Serve static content */
        if (!(S_ISREG(sbuf.st_mode)) || !(S_IRUSR & sbuf.st_mode)) {  // line:netp:doit:readable
            clienterror(fd, filename, "403", "Forbidden", "Tiny couldn't read the file");
            return;
        }
        serve_static(fd, filename, sbuf.st_size);                     // line:netp:doit:servestatic
    } else {                                                          /* Serve dynamic content */
        if (!(S_ISREG(sbuf.st_mode)) || !(S_IXUSR & sbuf.st_mode)) {  // line:netp:doit:executable
            clienterror(fd, filename, "403", "Forbidden", "Tiny couldn't run the CGI program");
            return;
        }
        serve_dynamic(fd, filename, cgiargs);  // line:netp:doit:servedynamic
    }
}
/* $end doit */

/*
 * read_requesthdrs - read HTTP request headers
 */
/* $begin read_requesthdrs */
void read_requesthdrs(rio_t *rp)
{
    char buf[MAXLINE];

    Rio_readlineb(rp, buf, MAXLINE);
    printf("%s", buf);
    while (strcmp(buf, "\r\n")) {  // line:netp:readhdrs:checkterm
        Rio_readlineb(rp, buf, MAXLINE);
        printf("%s", buf);
    }
    return;
}
/* $end read_requesthdrs */

/*
 * parse_uri - parse URI into filename and CGI args
 *             return 0 if dynamic content, 1 if static
 */
/* $begin parse_uri */
int parse_uri(char *uri, char *filename, char *cgiargs)
{
    char *ptr;

    if (!strstr(uri, "cgi-bin")) { /* Static content */  // line:netp:parseuri:isstatic
        strcpy(cgiargs, "");                             // line:netp:parseuri:clearcgi
        strcpy(filename, ".");                           // line:netp:parseuri:beginconvert1
        strcat(filename, uri);                           // line:netp:parseuri:endconvert1
        if (uri[strlen(uri) - 1] == '/')                 // line:netp:parseuri:slashcheck
            strcat(filename, "home.html");               // line:netp:parseuri:appenddefault
        return 1;
    } else { /* Dynamic content */  // line:netp:parseuri:isdynamic
        ptr = index(uri, '?');      // line:netp:parseuri:beginextract
        if (ptr) {
            strcpy(cgiargs, ptr + 1);
            *ptr = '\0';
        } else
            strcpy(cgiargs, "");  // line:netp:parseuri:endextract
        strcpy(filename, ".");    // line:netp:parseuri:beginconvert2
        strcat(filename, uri);    // line:netp:parseuri:endconvert2
        return 0;
    }
}
/* $end parse_uri */

/*
 * serve_static - copy a file back to the client
 */
/* $begin serve_static */
void serve_static(int fd, char *filename, int filesize)
{
    int srcfd;
    char *srcp, filetype[MAXLINE], buf[MAXBUF];

    /* Send response headers to client */
    get_filetype(filename, filetype);     // line:netp:servestatic:getfiletype
    sprintf(buf, "HTTP/1.0 200 OK\r\n");  // line:netp:servestatic:beginserve
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Server: Tiny Web Server\r\n");
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Content-length: %d\r\n", filesize);
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Content-type: %s\r\n\r\n", filetype);
    Rio_writen(fd, buf, strlen(buf));  // line:netp:servestatic:endserve

    /* Send response body to client */
    srcfd = Open(filename, O_RDONLY, 0);                         // line:netp:servestatic:open
    srcp = Mmap(0, filesize, PROT_READ, MAP_PRIVATE, srcfd, 0);  // line:netp:servestatic:mmap
    Close(srcfd);                                                // line:netp:servestatic:close
    Rio_writen(fd, srcp, filesize);                              // line:netp:servestatic:write
    Munmap(srcp, filesize);                                      // line:netp:servestatic:munmap
}

/*
 * get_filetype - derive file type from file name
 */
void get_filetype(char *filename, char *filetype)
{
    if (strstr(filename, ".html"))
        strcpy(filetype, "text/html");
    else if (strstr(filename, ".gif"))
        strcpy(filetype, "image/gif");
    else if (strstr(filename, ".png"))
        strcpy(filetype, "image/png");
    else if (strstr(filename, ".jpg"))
        strcpy(filetype, "image/jpeg");
    else
        strcpy(filetype, "text/plain");
}
/* $end serve_static */

/*
 * serve_dynamic - run a CGI program on behalf of the client
 */
/* $begin serve_dynamic */
void serve_dynamic(int fd, char *filename, char *cgiargs)
{
    char buf[MAXLINE], *emptylist[] = {NULL};

    /* Return first part of HTTP response */
    sprintf(buf, "HTTP/1.0 200 OK\r\n");
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Server: Tiny Web Server\r\n");
    Rio_writen(fd, buf, strlen(buf));

    if (Fork() == 0) { /* Child */  // line:netp:servedynamic:fork
        /* Real server would set all CGI vars here */
        setenv("QUERY_STRING", cgiargs, 1);                       // line:netp:servedynamic:setenv
        Dup2(fd, STDOUT_FILENO); /* Redirect stdout to client */  // line:netp:servedynamic:dup2
        Execve(filename, emptylist, environ);
        /* Run CGI program */  // line:netp:servedynamic:execve
    }
    Wait(NULL); /* Parent waits for and reaps child */  // line:netp:servedynamic:wait
}
/* $end serve_dynamic */

/*
 * clienterror - returns an error message to the client
 */
/* $begin clienterror */
void clienterror(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg)
{
    char buf[MAXLINE];

    /* Print the HTTP response headers */
    sprintf(buf, "HTTP/1.0 %s %s\r\n", errnum, shortmsg);
    Rio_writen(fd, buf, strlen(buf));
    sprintf(buf, "Content-type: text/html\r\n\r\n");
    Rio_writen(fd, buf, strlen(buf));
}
/* $end clienterror */
